Silicone compositions are used in an optical semiconductor sealing material and an optical waveguide material since characteristics such as transparency, heat resistance, and light resistance are excellent, and hardness and rubber elasticity are excellent. Among these, a methyl silicone composition has excellent durability such as heat resistance and light resistance. However, the silicone composition has a problem in which refractive index is low, an expansion coefficient is large, gas permeability is large, and adhesion to a substrate is low.
Then, by dispersing metal oxide particles such as zirconium oxide, titanium oxide, and silicon oxide into a silicone compound or combining these, these shortcomings are redeemed, and improvement in function is attained.
For example, a composition for coating a light emitting element obtained by combining fine particles of metal oxide and specific multifunctional polysiloxane (for example, see Patent Literature 1), a silicone resin compound containing zirconia nano particles which are surface-treated with an organosiloxane compound and a terminal alkoxysilyl group-containing silicone resin in which a chain length ratio of the organosiloxane compound and the silicone resin is in a specific range (for example, see Patent Literature 2), a silicone resin composition obtained by reacting metal oxide particles surface-modified with a vinyl terminal silicone-modified material and organohydrogen siloxane (for example, see Patent Literature 3), and a highly transparent silicone composition including silica particles obtained by grafting siloxane (for example, see Patent Literature 4) have been proposed.
In addition, a method of lowering viscosity to 100 Pa·s or less by combining three types of organic modifiers (Patent Literature 5) and a method of hydrophobization-treating inorganic oxide fine powder with an alkyl silazane compound (Patent Literature 6) have been proposed.